1. Technical Field
The present invention relates to a printing apparatus and a printing method.
2. Related Art
An ink jet printer includes a carriage on which a print head is mounted and discharges ink from the print head while moving the carriage along a predetermined main scanning direction. Due to this, the ink lands on a print medium, realizing printing. When the carriage moves along the main scanning direction, the carriage accelerates from a stopped state, subsequently moves at a constant velocity, and then decelerates to stop. The print head discharges ink during any one of these states of acceleration, constant velocity movement, and deceleration.
Furthermore, in the ink jet printer, when nozzles of the print head discharge ink, discharge of ink drops (main drops) is sometimes accompanied by discharge of drops smaller than main drops which are called satellites or the like. The satellites are also termed the subsidiary drops. Furthermore, in some cases, a discharged ink drop (main drop) partially breaks apart in the air to form subsidiary drops. A subsidiary drop can join a main drop in the air or can land at a position that overlaps the landing position of a main drop, so that the subsidiary drop may sometimes be substantially visually unrecognizable in the print result. On the other hand, a subsidiary drop may land apart from main drops on a print medium. Such a variation in the relation between the landing positions of a main drop and a subsidiary drop varies the area covered by the ink on the print medium and therefore affects the image quality of the print result.
Incidentally, JP-A-2010-280119 describes an ink jet recording apparatus in which air control windows provided at two ends of the movement range of the carriage are opened and closed by using shutters in accordance with the moving direction and acceleration/deceleration of the carriage so as to control the flow of air between the recording head and the recording medium.
Subsidiary drops are lighter in weight than main drops and therefore more strongly affected by airflows when flying. In the range in which the carriage can be moved, an acceleration region in which the carriage accelerates while moving and a constant velocity region in which the carriage moves at a constant velocity are different from each other in the quantity and speed of airflow that occurs between the carriage and the print medium. Therefore, in the related art, the positional relation between main drops and subsidiary drops at the time of landing is likely to differ between the acceleration region and the constant velocity region, so that density difference (density unevenness) sometimes occurs in print result between the two regions. For example, in the acceleration region, main drops and subsidiary drops tend to land in an overlapping state on the print medium whereas in the consent velocity region, main drops and subsidiary drops tend to land apart from each other on the print medium.
Furthermore, print results produced by the related-art ink jet printers sometimes exhibit a kind of image quality degradation that is called ripple. Concretely, as a nozzle discharges ink, swirling airflow occurs in the vicinity of the nozzle and affects the flight of the ink discharged from other nozzles so that their landing positions deviate. Such deviation results in color deviation or unevenness being visually recognized as a kind of image quality degradation (ripple).
Note that the ink jet printer of JP-A-2010-280119 mentioned above, because of using detour spaces at the two ends of the movement range of the carriage, can be said to be able to achieve the advantageous effects only by moving the carriage to the two ends so as to use the air flowing between the detour spaces and the movement range. Furthermore, because JP-A-2010-280119 provides detour spaces at the two ends of the movement space of the carriage, the drawback of increasing the transverse width of the apparatus is conceivable regarding this technology.